RAD51 Associated Protein 1 (RAD51AP1)

RAD51AP1 specifically stimulated joint molecule formation through structure-specific DNA binding and physical contact with RAD51. RAD51AP1 was required to protect HeLa cells from agents that cause DNA double-strand breaks. At the biochemical level, RAD51AP1 had selective affinity for branched DNA structures, and it stimulated D loop formation by RAD51, a pivotal step in recombination.

The predicted PIR51 protein has 335 amino acids and a calculated pI of 9.95. The authors suggested that PIR51 is the human homolog of mouse Rab22 since the 2 proteins share 63% sequence identity. Northern blot analysis revealed that PIR51 is expressed as a 2.4-kb mRNA in human testis and thymus, and at lower levels, in colon and small intestine.